Atmospheric injection of reflective aerosol for mitigating global warming

ABSTRACT

A method is provided for mitigating global warming. In such method, fine particles can be injected or dispersed into the stratosphere. The particles can be characterized by relatively low emissivity in the visible spectrum and relatively high emissivity at thermal infrared wavelengths. In a particular embodiment, the fine particles can consist predominantly of silica. In a particular embodiment, the fine silica particles can include diatomaceous earth (DE), which may or may not be heat treated before injection and dispersal within the stratosphere. In one embodiment, the fine silica particles can include at least one of silica fume, fumed silica, or powdered quartz. The fine silica particles may have an average diameter ranging between 5 nanometers and 100 microns.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application61/194,709 filed Sep. 30, 2008 entitled “APPLICATIONS OF STRATOSPHERICLEVEL REFLECTIVE AEROSOL DEPOSITION IN MITIGATING THE EFFECTS OF GLOBALWARMING”, the disclosure of which is hereby incorporated by referenceherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to geoengineering and more specifically toa method for mitigating global warming through injection of an aerosolsuch as particles into the atmosphere.

2. Description of the Related Art

The recent increase in global temperatures is changing the world'sclimate in unpredictable and damaging ways. No matter what the cause,whether it is because of natural factors or just simply a man-madeconsequence of an industrial society, the one degree Fahrenheit observedincrease in global temperature has already caused incalculable damagesto tropical and Arctic climates. Since 1980, the Sahara has expandedover a hundred miles. (Tucker) In summer 2007, Arctic sea ice retreatedfrom land to its farthest extent ever; by 2020 the ice may completelydisappear each summer. Tropical cyclones are becoming stronger and morefrequent. In 2008, 100,000 perished from the cyclone in Myanmar. It maytake a lifetime for New Orleans to recover from 2005's HurricaneKatrina. Once growing plentiful harvests, farmers are now impacted morefrequently by both severe droughts and flooding.

Bleak predictions from the Intergovernmental Panel on Climate Change(IPCC) point to dangerous consequences for inaction. An estimated threeto eight degree increase in mean global temperature will cause a rise insea level that inundates and displaces hundreds of millions worldwide,melt remaining Arctic permafrost, intensify hurricane devastation, anddisrupt weather patterns. (Spotts) Moreover, a relatively small changein global temperature might provoke much greater changes, known asrunaway global warming, due to positive feedback events. For example,the rapid melting of Arctic sea ice wipes out reflective ice cover aboveocean waters, thus increasing the ocean absorption of solar energy bythe Arctic Ocean on a planetary scale. The thawing of permafrost regionsreleases unfathomable quantities of carbon dioxide and methane into theatmosphere and could greatly amplify global warming. (Yarris)

International agreements such as the Kyoto protocol seek to reduceman-made carbon dioxide emissions, but it is doubtful whether suchmeasures will suffice. Scientists today suggest that only reducingfossil fuel use will not prevent catastrophic damage to global climates.(Joyce) Others warn that unless carbon dioxide is removed from theatmosphere, the warming will not stop. (Yarris) However, such a cleanupproject to reclaim unfathomable amounts of carbon dioxide would beenergy-demanding and almost double current energy costs. (Thambimuthu)

Recent scientific studies have demonstrated that there might be asecondary cause to global warming separate and apart from increasedgreenhouse gas emissions. In 2005, an article in Science cited surfaceobservations from the Baseline Surface Radiation Network (BSRN) showingthat solar radiation observed at the Earth's surface increased by 6.6W/m−2 between 1985 and 2000. (Wild, 849) In other words, this period hasbeen marked by “global brightening.” Since, on average, light emittedfrom the sun does not increase, the planetary albedo, or the overallreflectivity of the Earth, must have decreased during this period.(Wild, 848) With decreased albedo, the Earth absorbs more solar energy.Greater absorbed solar energy has caused the mean global temperature torise rapidly since 1985.

At the same time, temperatures in the Earth's stratosphere are proven tohave actually decreased between 1980 and 2000 by an unprecedented 0.7degree Celsius. (USGCRP) It is likely that the two events are related.Lower temperatures in the stratosphere signals lower solar energyabsorption there. As the stratosphere absorbs less solar energy, moresolar energy reaches the Earth's surface to cause global warming. Thisobserved correlation is a starting point for this study.

U.S. Pat. No. 5,003,186 to Chang et al. (the Chang patent) discusses amethod of depositing fine particles in the stratosphere to reduce globaltemperatures. The Chang patent describes seeding the stratosphere withparticles that have relatively low emissivity in the near-infraredspectrum and high emissivity in the far infrared and visible spectrums.“Emissivity” is a measure of how much light energy an object absorbs.Because the particles have high emissivity in the visible spectrum, themethod proposed by the Chang patent could decrease the amount of visiblelight reaching the Earth's surface. This, in turn, would be undesirableif found to affect fundamental ecological processes such as chemicalcycling, energy flow, and photosynthesis.

SUMMARY OF THE INVENTION

According to an aspect of the invention, a method is provided formitigating global warming. In such method, fine particles can beinjected or dispersed into the stratosphere. The particles can becharacterized by relatively low emissivity in the visible spectrum andrelatively high emissivity at thermal infrared wavelengths.

In a particular embodiment, the fine particles can consist predominantlyof silica. In a particular embodiment, the fine silica particles caninclude diatomaceous earth (DE), which may or may not be heat treatedbefore injection and dispersal within the stratosphere. Heat treatmentcan affect the content of crystalline silica in the DE. Typically, withtreatment by high heat, the DE may contain greater than 50% crystallinesilica at time of the injection into the atmosphere.

In one embodiment, the fine silica particles can include at least one ofsilica fume, fumed silica, or powdered quartz. The fine silica particlesmay have an average diameter ranging between 5 nanometers and 10microns. The fine particles may closely resemble a composition ofvolcanic ash, such that they have optical and physical propertiessimilar to volcanic ash.

A method is provided for mitigating global warming in accordance with anembodiment of the invention. Such method can include injecting ordispersing fine silica particles into the stratosphere. The particlesare dispersed in a concentration sufficient to cause statisticallysignificant warming of the stratosphere. A statistically significantcooling of the troposphere can also occur simultaneously with thewarming of the stratosphere.

In another embodiment of the invention, the fine silica particles may beheated so as to lower the surface area of each particle. This heatingwould occur in such a way as to limit the amount of surface area thatthe particles would add to the stratosphere. The particles would betreated so as to limit the addition of surface area available forsurface-based chemical reactions, including limiting the surface areaavailable on each particle for conversion of chlorine compounds intoactivated chlorine. In such way, possible effects of the particles onthe ozone layer of the upper atmosphere would be limited.

In another embodiment of the invention, the fine silica particles arecoated by a chemical protective layer that inhibits chemical reactionsfrom occurring at surfaces of the particles in the stratosphere.

The fine silica particles may have an average diameter ranging between 5nanometers and 10 microns. In a particular embodiment, the averagediameter may be below 5 microns.

In a particular embodiment, the fine silica particles can includediatomaceous earth. In another embodiment, the fine silica particlesinclude at least one of silica fume, fumed silica, or powdered quartz.

A particular embodiment provides for injecting or dispersing fineparticles in the stratosphere, the particles having spectral propertiessimilar to at least one material selected from the group consisting ofsulfate aerosols or sulfuric aerosols.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph comparing the world carbon dioxide production withglobal sulfur dioxide emissions.

FIG. 2 is a graph of the global temperature anomaly since 1880.

FIG. 3 is a graph illustrating a transmittance, emissivity plot forsulfuric acid (H2SO4) aerosols.

FIG. 4 is a graph illustrating a transmittance plot for diatomaceousearth.

FIG. 5 is a graph overlaying a transmittance plot for sulfuric acid(H2SO4) aerosols with a transmittance plot for diatomaceous earth.

FIG. 6 is a graph showing particle distributions in atmospheric samples.

FIG. 7 is a reflectance plot for powdered quartz aerosols between 0 and75 microns.

DETAILED DESCRIPTION

More powerful measures may be needed than simply switching toalternative fuels to actively combat global warming without harming theenvironment or the economy. Herein, a geo-engineering solution isproposed for addressing the current global warming crisis. Abrupt globaltemperature decreases following the eruptions of Mount Saint Helens in1980 and Mount Pinatubo in 1991 suggest that the presence of reflectiveaerosols in the stratosphere could reduce global warming. Differentcandidate aerosols are available for injection into the stratospherewhich can be demonstrated to reflect visible and infrared wavelengths oflight. A suitable aerosol material is in relative abundance on Earth andcan be obtained relatively inexpensively and have minimal impacts onecosystems worldwide.

An agent capable of inhibiting global warming may have already beenidentified and may have already been responsible for keeping globaltemperatures from increasing during much of the period before thepresent. However, the agent that may have been at work was sulfuricaerosols which are a component of air pollution. Their effect as anagent in inhibiting global warming may be lessening now. While otherfactors cannot be definitively ruled out, increased global warming since1980 has occurred simultaneously with global reductions in air pollutionduring this period, particularly in sulfuric aerosol pollution. Theatmospheric concentration of sulfuric aerosols shows a decrease of up to50% in urban areas between 1980 and 1999, particularly in North Americaand Europe.

Sulfuric acid, or H2SO4, is produced when burning fossil fuels and canbe found in smog, or a type of air pollution sometimes seen at lowerlevels of the atmosphere. Smog pollution can sometimes be found atground level or not far above ground level in large cities or otherareas where large amounts of fossil fuels are burned. Sulfuric acid is aclear liquid in dilute solutions and is tinged with yellow inconcentrated solutions. When sulfuric acid is exposed to air, it makes afine mist of sulfuric aerosols. Onions are one example where sulfuricacids can make sulfuric aerosols.

While dilute sulfuric acid is a clear liquid, sulfuric aerosols havespectral properties different from the acid itself: they absorbwavelengths of far-infrared light. Far infrared light, defined as lightof wavelengths between 8 to 14 μm, is primarily responsible for thermalradiation. When far-infrared light strikes the Earth's surface, it isabsorbed and converted into thermal energy which heats the Earth'satmosphere. Since sulfuric aerosols absorb far-infrared light, theyprevent some of the far-infrared light from reaching the surface.Because they absorb thermal energy from far-infrared light before it canreach the Earth's surface, sulfuric aerosols also raise the temperatureof the surrounding medium in accordance with the law of Conservation ofEnergy.

For sulfuric aerosols to decrease global temperatures, a few conditionsmust be met. First, the sulfuric aerosols must be present in thestratosphere, a layer of the atmosphere above the lowest atmospherelayer, the troposphere, so that the absorbed solar energy can bedirected away from the surface. Already, sulfuric aerosols emitted byvolcanoes and fossil fuels collect in the troposphere, but some amountmakes its way to the stratosphere. Second, the sulfuric aerosols must berelatively abundant in order to absorb enough thermal energy to make adifference.

By this process, sulfuric aerosols are capable of increasing planetaryalbedo by absorbing far-infrared energy in the stratosphere andreradiating it back into space. The lack of a significant globaltemperature rise in the sulfur-laden atmosphere prior to 1980 suggeststhat the injection of sulfuric aerosols into the stratosphere couldmitigate the effects of global warming. FIG. 1 shows that sulfur dioxideproduction stayed at close to a 1:1 ratio with carbon dioxide productionuntil about 1980, when the ratio of carbon dioxide to sulfur dioxideincreased. FIG. 2 shows that global temperatures remained close tolong-term average (such average being indicated at 0.0° C. on thevertical scale) until about 1980, when the global temperature began torise steadily and rapidly. One interpretation of the data would lend tothe conclusion that sulfur dioxide production before 1980 shielded theearth from global warming, and that the reduction in sulfur emissionsrelative to carbon emissions led to an increase in the globaltemperature above the average. This would suggest that climate changecorrection would entail simply the addition of sulfur dioxide, in largequantities, to the atmosphere. However, harmful impacts uponenvironmental and human health from sulfuric aerosols caution againsttheir purposeful injection into the atmosphere for mitigating globalwarming. Furthermore, a more precise, controlled injection of particlesthat can initiate global cooling can be performed with effects 100 timesor more above than the cooling effects of untargeted sulfur dioxideemissions.

By simulating an atmosphere similar to that of Earth, experimentationdemonstrates that the dispersion of certain types of particles couldcause a change in mean atmospheric temperatures. Silica is a type ofmaterial which has been identified as a candidate for injection into theatmosphere to decrease global albedo, and hence, reduce global warming.

Silica is among the most common minerals on Earth. Silica, an oxide ofsilicon, is commonly found in sand and glass. Silica is also foundnaturally in very small particles in form of diatomaceous earth (DE). DEearth includes fossilized remains of diatoms, a type of hard-shelledalgae. Particles can range from 1 to 100 microns in width. As found innature, diatomaceous earth contains mostly amorphous silica. Amorphoussilica is an efficient absorber of liquids, and for this reason, can beused as a drying agent. In some cases, DE can be obtained in which theaverage particle width is less than or equal to about 10 microns. Whentreated by high heat in a “calcining” process, DE can become mostlycrystalline in form, having a crystalline content of greater than 50%,and typically 60% or more. Heat treated DE is commonly used as a waterfiltering agent. Among other silicates which can have fine particles arefumed silica, silica fume, and powdered quartz. Silica has spectralproperties close to those of sulfuric aerosols, which, in previousabundance, appear to have inhibited global warming. Silica particles,including diatomaceous earth, have particle sizes which are capable ofremaining suspended in the atmosphere for a number of years withoutcausing noticeable environmental impact.

NASA studies following the June 1991 eruption of Mt. Pinatubo observed aglobal temperature decrease of 0.6 degrees Celsius (one degreeFahrenheit) between 1991 and 1992. (Ritchie, 178) The eruption involveda massive injection of volcanic ash in the atmosphere. A commoncomponent of volcanic ash, silica aerosols, are microscopic (usuallyhaving particles from 0.01 to 10 microns in diameter). The eruption mayhave provided sufficient energy to inject fine silica aerosols into thestratosphere. The fine silica aerosols included particles having a sizesmall enough to be suspended by stratospheric winds for an extendedperiod of time. Thus, the injection of fine silica aerosols into thestratosphere may be the reason for the global cooling event followingthe eruption.

The possibility of reversing global temperature increases bystratospheric injection of fine particles having spectral propertiessimilar to sulfuric aerosols can be demonstrated. Silica, such as fumedsilica, silica fume, powdered quartz, or diatomaceous earth, amongothers, can have the correct properties. Such materials are extremelyfine powders that are in relative abundance on Earth. Silica absorbs thesame frequencies of light as sulfuric aerosols do.

FIGS. 3 and 4 are plots of transmittance for each of sulfuric acid(H2SO4) and DE. Each shows similar thermal emissivity. As demonstratedby a combination of the data from each plot (FIG. 5) it is clear thatH2SO4 aerosols and diatomaceous earth (a form of silica) have similaremissivity in the thermal range. FIG. 5 shows an emittance plot of 75%H2SO4 in Aerosol Solution and Diatomaceous Earth comparing thefar-infrared wavelength (8 to 20 μm) to the total emittance (orabsorption). Emittance is a measure of how much light energy an objectabsorbs. DE exhibits properties very similar to sulfuric aerosols in thefar-infrared range: for instance, both have relatively high emittancenear 9 μm and low emittance near 14 μm. Data shown on FIGS. 3, 4 and 5are found in external references: De Freitas, and NASA Astrophysics.

This means that silica aerosols can be used to mimic the cooling effectsof sulfuric aerosols in the stratosphere. Silica aerosols such as DE canalso increase cloud albedo by acting as a nucleation site for waterdroplet formation. By increasing cloud albedo, more solar energy will beradiated into space. Finally, silica aerosols such as DE do not reactwith many naturally-occurring chemicals and do not break down whenexposed to UV radiation. Since silica aerosols are made up of tinyparticles of silicon dioxide, the aerosol is indistinguishable with sandwhen it falls back to the Earth.

Silica aerosols have relatively low emissivities in the visible and nearinfrared spectrum and comparable emissivity in the far infrared spectrumto sulfate aerosols. Therefore, silica aerosols could be used to remove“thermal” far infrared light in a targeted way to cause global coolingwithout substantially impacting the amount of visible light that reachesthe surface of the Earth.

U.S. Provisional Application 61/194,709, incorporated by referenceherein, demonstrates that a suspension of DE in a medium can decrease arate at which a surface disposed below the medium warms in response tolight of visible and thermal wavelengths. The experimental workdemonstrates with confidence that diatomaceous earth can cause adecrease in mean surface temperatures for time periods equal to andbeyond the testing period. In light of this demonstration, silicaaerosols, when dispersed in sufficient quantity into the stratospherecan be expected to cause demonstrable and significant change in meanglobal surface temperature of the Earth.

These silica aerosols, like the sulfuric aerosols, added significantsurface area to the stratosphere, which was seen dramatically during thevolcanic eruption of Mt. Pinatubo in 1991. Sulfuric aerosols along withfine particulate volcanic ash added reaction sites for the conversion ofinactivated chlorine compounds into activated chlorine. This activatedchlorine, usually in the form of a free radical, can break down ozone(O₃) into diatomic oxygen and free oxygen ions. The breakdown of theozone layer caused by this type of a reaction in undesirable because ofits effects in shielding the Earth's surface from harmful ultravioletradiation that exists in outer space and the upper atmosphere. The ozonelayer is one of the most protected areas of the Earth's atmosphere as itfilters all incoming solar radiation and removes harmful UV light whichcan harm both plants and animals alike. This UV radiation is alsoparticularly harmful to humans and can cause cancer and in rare casesbirth defects.

To help avoid unwanted effects of stratospheric particles on the ozonelayer two methods are proposed. One possibility is to heat the particlesbefore injection to a temperature just high enough to reshape theparticles by smoothing out rough or jagged pockets at the surface ofeach particle where reactions can take place. In one embodiment, theprocess could be conducted in the presence of a dopant such as boron,which might further assist in lowering the glass transition temperatureof the particle composition, and possibly helping to smooth the shape ofthe resulting particles. For example, a “boronating” process could beconducted. The process could be conducted in a way that makes theparticles more spherical and standardized, and possibly even morestandardize in size. In that way, the amount of surface area added bythe particles to the stratosphere could be closely measured andmonitored.

Another possibility is that fine silica particles could be used togetherwith a chemical inhibitor which inhibits reaction with ozone. Forexample, a chemical inhibitor such as calcium hydroxide or calcium oxidecould be mixed with or applied to particles prior to their dispersal inthe atmosphere. Such inhibitors can include, which can combine withfree, activated chlorine to make harmless compounds that are trappedwithin the particle or which return to the surface, such as in form ofrain water. The size of the particle has a direct effect on theresidence time of the particle in the stratosphere. “Residence time” istraditionally defined as the amount of time a small aerosol particle canstay aloft in the atmosphere and is usually measured by observing theconcentration of the particle in the atmosphere after a number of days,months, or years have elapsed. For the particles to have a desiredeffect in mitigating global warming, the residence time of particlesshould be sufficiently long to provide stable long-term residence in thestratosphere. However, the residence time should not be too great, inorder to allow for up or down adjustment of the cooling effect intrending towards or maintaining a desired long-term result. With adesired residence time, the particle concentration could be allowed todecrease so that, in times of uncontrolled global cooling events, suchas volcanic eruptions and natural variations in solar output, theclimate effects of these natural events would be reduced.

Particles with different sizes have different residence times because oftheir specific gravity, a measure of their mass against their surfacearea. Particles with low surface area and high mass have lower residencetimes than particles with high surface area and low mass. Another factorto consider when engineering residence time is the particle's ability tocondense into larger particles. For instance, particles under 0.05microns typically stick together in the atmosphere and create largerparticles that can then fall out of the atmosphere at a higher rate.FIG. 6 is a graphing showing distributions of particle sizes as measuredin four different samples conducted at different atmospheric locations.Curves labeled 1 and 2 show the particle distributions at locations farfrom emissions of particle matter. The curves labeled 3 and 4 show theparticle distributions at locations near sources of particle emissionsThe curves demonstrate that particles can be found which persist in theatmosphere which range between 0.01 microns and 100 microns in size, andwhich are more commonly seen between about 0.02 microns and 20 microns,as represented on the logarithmic scale of FIG. 6. From the figure, itis apparent that particles having sizes near 0.2 microns or near 4microns are in greatest abundance in each of the distributions found inthe atmospheric samples. This may indicate that particles of these sizestend to persist in the atmosphere for relatively long periods of time.Thus, it may be desirable to inject particles having these sizes intothe stratosphere to achieve a desirable residence time. Therefore, theparticles could have sizes mostly between about 0.2 microns and about 10microns, or be even more closely distributed with most particles havingsizes between about 0.5 microns and about 5 microns. It might even bebeneficial to engineer silica particles to have average particle sizenear 0.2 and 4 microns.

Another factor that could be considered when engineering the particlesis the particles' relative abilities to effloresce and deliquesce.Efflorescence is defined as a material's ability to lose watertraditionally in its crystalline form at certain temperatures andpressures. Deliquescence is the compounds ability to absorb water intoits crystalline structure at certain temperatures and pressures. It maybe beneficial to use a type of silica or diatomaceous earth that hasefflorescent and deliquescent properties similar to volcanic aerosols,so as to more closely mimic a global cooling effect that has beenobserved after volcanic eruptions. It is possible that deliquescentparticles are a source of cloud condensation nuclei (CCN) which cancontribute to the formation of clouds in the stratosphere. Thus, thesilica particles might function as CCNs to provide surfaces on whichwater vapor molecules condense and form clouds in the stratosphere. Theformation of stratospheric clouds may provide an additional way toreflect some incoming sunlight before it reaches the lower atmosphereand, thus, help mitigate the warming effect caused by greenhouse gases.

Alternatively, in a particular embodiment, particles could be selectedwhich effloresce readily but which do not deliquesce or do notdeliquesce much. Using such particles, one could deliberately limit theeffect of the particles on the formation of stratospheric clouds. Thiscould be one way of controlling or reducing the formation ofstratospheric clouds so as to control or limit the reduction in visiblelight to the Earth's surface.

Silica aerosols can be injected into the stratosphere using a variety ofmeans. Silica particles in form of DE, fumed silica, silica fume,powdered quartz or other material could be injected into the atmosphereduring the fuel combustion and exhaust production processes ofhigh-flying aircraft. FIG. 7 is a graph illustrating reflectance forpowdered quartz. For example, without limitation, the aerosol could beprovided as an additive to a combustion or after-combustion process ofan aircraft engine in flights entering the stratosphere (typically ataltitudes above 35,000 feet). Alternatively, separate from a combustionprocess, the aerosol could be metered out through dedicated equipmenttherefore.

The process may be controlled so as to inject the aerosol when theaircraft is at a location within the atmosphere that leads to dispersionof a large amount of the aerosol in the stratosphere. The process mayalso be controlled so as to not disperse the aerosol when the aircraftis at a location that leads to dispersion of a large amount of theaerosol in the troposphere. The altitudes at which the aerosol injectioncan be performed can vary with latitude, seasonal weather patterns, andeven local weather patterns and weather events. The site of particleinjection can be selected in accordance with latitude as well. A greateramount of sunlight typically reaches the Earth at low latitudes.Therefore, aerosol injection into the stratosphere at low latitudes(tropical and subtropical) can be expected to directly block a greateramount of sunlight than at middle latitudes and at high latitudes beyondthe Arctic and Antarctic Circles. However, aerosol injection in themiddle and high latitudes might also help mitigate global warming, forexample, if it caused the rate at which ice and snow melts to decreasedue to decreased warming from sunlight. In that case, more snow and icewould remain available at the middle and higher latitudes to reflectsunlight back into space. The same effect could also occur if thedispersal of the silica aerosol were to increase the rate of snow andice accumulation in the middle and higher latitudes.

Other possible ways of injecting silica aerosols into the stratosphereinclude launching of high-altitude balloons carrying the particles andequipment for dispersing the particles into the surrounding air. Rocketsmight also be used to carry the particles into the stratosphere. Theremay be still other ways in which silica aerosols can be injected intothe atmosphere.

From the foregoing it is demonstrated that silica aerosols includingdiatomaceous earth can be a global warming inhibitor when dispersed intothe stratosphere in sufficient quantities. The magnitude of a decreasecan mitigate the effects of global warming while the aerosol remainspresent in the stratosphere.

While the invention has been described in accordance with certainpreferred embodiments thereof, those skilled in the art will understandthe many modifications and enhancements which can be made theretowithout departing from the true scope and spirit of the invention, whichis limited only by the claims appended below.

1. A method of mitigating global warming comprising injecting fineparticles in the stratosphere, the particles characterized by relativelylow emissivity in the visible spectrum and relatively high emissivity atthermal infrared wavelengths.
 2. A method as claimed in claim 1, whereinthe fine particles consist predominantly of silica.
 3. A method asclaimed in claim 1, wherein the fine silica particles includediatomaceous earth.
 4. A method as claimed in claim 3, wherein thediatomaceous earth contains greater than 50% crystalline silica at timeof the injection into the atmosphere.
 5. A method as claimed in claim 1,wherein the fine silica particles include at least one of silica fume,fumed silica, or powdered quartz.
 6. A method as claimed in claim 1,wherein the fine silica particles have average diameter ranging between0.01 and 10 microns.
 7. A method as claimed in claim 1, wherein thecomposition of the fine particles closely resembles a composition ofvolcanic ash.
 8. A method as claimed in claim 1, wherein the particlesare designed in such a way that the particle size maximizes theirresidence time aloft in the stratosphere.
 9. A method as claimed inclaim 1, wherein the particles have average sizes of 0.2 microns and 4microns.
 10. A method as claimed in claim 1, wherein the composition ofthe fine particles closely resembles a composition of volcanic ashinjected into the stratosphere by the 1991 eruption of Mount Pinatubo,Philippines.
 11. A method of mitigating global warming comprisingdispersing fine silica particles in the stratosphere.
 12. A method asclaimed in claim 1, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 13. Amethod as claimed in claim 11, wherein the fine silica particles includediatomaceous earth.
 14. A method as claimed in claim 11, wherein thefine silica particles are heated as to lower their surface area.
 15. Amethod as claimed in claim 11, wherein the fine silica particles arecoated by a chemical protective layer that inhibits chemical reactionsalong the surface of each particle in the stratosphere.
 16. A method asclaimed in claim 15, wherein the chemical protective layer includes atleast one of calcium hydroxide or calcium oxide.
 17. A method as claimedin claim 11, wherein the fine silica particles include at least one ofsilica fume, fumed silica, or powdered quartz.
 18. A method as claimedin claim 11, wherein the fine silica particles have average diameterranging between 0.01 microns and 10 microns.
 19. A method as claimed inclaim 11, wherein the fine silica particles are treated so that they caneffloresce readily and have no more than low deliquescence, such thatthe particles inhibit the formation of cloud condensation nuclei. 20.(canceled)
 21. A method of mitigating global warming comprisingdispersing fine particles in the stratosphere, the particles havingspectral properties similar to at least one material selected from thegroup consisting of sulfate aerosols or sulfuric aerosols.
 22. A methodas claimed in claim 2, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 23. Amethod as claimed in claim 3, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 24. Amethod as claimed in claim 4, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 25. Amethod as claimed in claim 5, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 26. Amethod as claimed in claim 6, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 27. Amethod as claimed in claim 7, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 28. Amethod as claimed in claim 8, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 29. Amethod as claimed in claim 9, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 30. Amethod as claimed in claim 10, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.
 31. Amethod as claimed in claim 11, wherein the particles are dispersed in aconcentration sufficient to cause statistically significant warming ofthe stratosphere and statistically significant cooling of thetroposphere simultaneous with the warming of the stratosphere.